ABNORMALITIES OF AUDITORY EVENT-RELATED POTENTIALS IN SCHIZOPHRENIA PRIOR TO TREATMENT

Background: P300 amplitude reduction is a consistent finding in schizo phrenic patients, but it is unclear if this abnormality predates neuro leptic treatment or is present at onset of illness. Methods: Auditory event-related potentials (ERPs), during a standard oddball paradigm, w ere recorded from 45 neuroleptic-naive schizophrenics, 56 drug-free, p reviously treated schizophrenics, and 73 healthy normal controls, Fort y-seven of the schizophrenic subjects had their first episode within t he past year. Results: N200 amplitude did not differ among groups. P30 0 amplitude was significantly smaller in both neuroleptic-naive and pr eviously treated schizophrenic groups compared to the control groups. There were no significant differences between the two schizophrenic gr oups in P300 amplitude. N200 and P300 latency were prolonged in previo usly treated schizophrenics compared to neuroleptic-naive schizophreni cs and normal controls. Conclusions: The present study suggests that E RP abnormalities, especially P300 amplitude reduction, are already pre sent prior to the administration of neuroleptic medication in the earl iest stage of schizophrenia. (C) 1998 Society of Biological Psychiatry .